TONIGHT'S MUST-SEE

"Men in Trees," 7 and 8 p.m., ABC. This fun show debuted Tuesday, before settling into its regular spot at 8 p.m. Fridays. If you missed the opener, catch it at 7 p.m. And you might want to skip the next few paragraphs. As the second hour begins, Marin (Anne Heche) realizes she's not much of a relationship expert, after all. She'll stay in little Elmo, Alaska, while rethinking her life. Few of these Elmo folks want advice, but she has two fans. One is Patrick, who has a radio show; the other is Annie, who followed her here from New York and now gets a job and an apartment. Tonight, Patrick has Marin on his show and asks Annie for a date. Theresa, the former rock singer, is still living with Ben (the giant Abraham Benrubi), but has a date with someone else. And Marin, the expert, remains perplexed.

OF NOTE

"Cheaper By the Dozen" (2003), 5 p.m., TBS. A lightweight story, emphasizing sight gags, is propped up by an appealing cast. Steve Martin and Bonnie Hunt play the parents, with Hilary Duff and Tom Welling as two of their 12 kids.

"Avatar: Secret of the Fire Nation," 5 p.m., Nickelodeon; reruns at 5 p.m. tomorrow and 1 p.m. Sunday. The animated series expands to an hour for this tale. Escorting refugees, Aang passes through Serpent's Pass and sees an evil invention that could destroy the wall protecting the city.

"Ghost Whisperer," 7 p.m., CBS. This wraps up the two-part season finale. Melinda, already troubled, is overwhelmed by a plane crash. There are hundreds of souls for her to help; there's also a mysterious stranger, trying to gather them into some sort of evil force.

"Cheetah Girls 2" (2006), 8 and 9:45 p.m., Disney Channel. The songs are bouncy and the Barcelona settings are appealing. The plot is lame — with problems appearing and disappearing arbitrarily — but the characters aren't as hyper as they were in the original.

"Las Vegas," 8 p.m., NBC. As a wedding nears, people gather. Guest stars include Dean Cain, Jerry O'Connell, Shawn Christian, Wolfgang Puck and country's Sugarland.

"Celebrity Duets," 8 p.m., Fox. Someone is ousted, trimming the field to five.

"Close to Home," 8 p.m., CBS. Kids claim they killed a man in self-defense, because he was an Internet predator.

"Numb3rs," 9 p.m., CBS. Charlie has odd dreams involving his mother. Meanwhile, Don studies two terribly similar deaths.

"Law & Order," 9 p.m., NBC. This is the rerun that was announced for last week, then delayed. When an undercover cop is killed, police try to learn who leaked the identity.